The scientific name for yellow baboons comes from the Greek words kynos
and kephalikos, meaning dog and head, respectively. This moniker refers to
the quadrupedal stance
seen in all baboons as well as the elongated muzzle which makes baboons look
like dogs compared to most other monkeys and apes, including humans, which have
flat faces (Altmann & Altmann 1970). While Groves (2001) recognizes
P. cynocephalus to be a separate species from other baboons, some taxonomists
have suggested that all yellow baboons be classified as a subspecies of
P. hamadryas (Jolly 1993).

MORPHOLOGY

Yellow baboons are aptly named for the yellow-brown fur which covers their
bodies except for their undersides, including the inner surfaces of the limbs,
cheeks, and patches of fur on either side of the muzzle, which are white (Rowe
1996; Groves 2001). Adult males and females have longer hair along their flanks
compared to the rest of their bodies while males have longer fur at the nape
of their necks (Groves 2001). Yellow baboons have a prominent brow ridge covered
in yellow-gray fur, but the rest of their face appears black and is only finely
covered with fur. Their ischial callosities are also black. They have a protruding
muzzle, similar to a dog's. Yellow baboons walk quadrupedally, with their
tails held up slightly and curved away from the body. There is variation between
subspecies in the tail position and shape (Groves 2001). All baboons are sexually dimorphic. Wild yellow baboon males have an average height of 1200 mm (3.94
ft) and weigh 25.8 kg (56.9 lb) while females measure 976 mm (3.20 ft) and
weigh only 11.0 kg (24.3 lb), on average (Altmann et al. 1993). Variation in
length and sharpness of canine teeth is also seen among males and females.
Male baboons have long, sharp upper canine teeth compared to females. They
use their canines in aggressive interactions with other males and when feeding on large vertebrate prey (Walker 1984; Altmann pers. comm.).

Subspecific differences are slight among yellow baboons. Papio cynocephalus
cynocephalus infants are born with a black natal
coat that changes to
the adult coloration as they age, while P. c. kindae infants
have red coats at birth and P. c. ibeanus are
born white (Groves 2001; Jolly & Phillips-Conroy 2005). Young baboons lose
their natal coat starting at six months of age and have adult coloration by
the end of month nine (Altmann pers. comm.). Other differences between subspecies include
tail shape, body size, and pelage color. "Broken tails" are seen in P. c. cynocephalus;
the tail is held almost horizontally away from the body and then falls abruptly,
appearing broken. The other species have more gently curved tails. Differences
in body size between subspecies can be seen in P. c. kindae,
which is much smaller than other subspecies. Papio cynocephalus kindae males
are about the same size as females of the other two subspecies and the females
are proportionately smaller than the males (Jolly 1993). Finally, unlike the
other subspecies, P. c. ibeanus has wavy instead
of straight body hair (Groves 2001).

Like other cercopithecines, yellow baboons have cheek pouches, sacs in the
lower portion of the cheek wall that can be used to store food. Moving between
the cheek pouch and the oral cavity through a slit-like opening, food can be
stored in the cheek pouch for consumption at a later time (Lambert & Whitham
2001).

Longevity in wild female yellow baboons is estimated to be around 14 to 15
years, but females have been recorded living up to 27 years in the wild (Rhine
et al. 2000). Because of their social system and patterns of dispersal, it
is more difficult to estimate male longevity in the wild (Altmann et al. 1988).
The maximum lifespan in captivity is 40 years (Ross 1991).

RANGE

Yellow baboons are found in central Africa from the west to eastern coasts
in Angola, Zambia, Malawi, Mozambique, Tanzania, Kenya, and Somalia (Groves
2001). From east of the Luangwa River in Zambia, into Malawi, northern Mozambique,
and most of Tanzania, P. c. cynocephalus can be found.
Papio cynocephalus ibeanus is found in Kenya and southern
Somalia and may range into southeastern Ethiopia while P. c. kindae is
found in eastern Angola, southwestern Zambia, and parts of southern Democratic
Republic of Congo (Jolly 1993; Groves 2001). There are some areas of overlap
in the range of P. cynocephalus and other baboon (Papio) species,
but levels of hybridization differ. For example, in Zambia and Angola, P. c. kindae overlaps with P. ursinus subspecies but there is not evidence of
interbreeding (Jolly 1993). On the other hand, in Kenya, P. c. ibeanus overlaps
with P. anubis and forms a hybrid zone, an area in which
individuals show unusual phenotypic diversity resulting from ongoing crossbreeding
between species (Samuels & Altmann 1986; Alberts & Altmann 2001). The
crossbreeding of P. cynocephalus and P. anubis in
this area may have contributed to the formation of the
subspecies P. c. ibeanus (Alberts & Altmann 2001).

Long-term research on yellow baboons has been conducted since 1971 by Jeanne
and Stuart Altmann, Susan Alberts, and their colleagues at Amboseli National
Park, in southern Kenya on the border of Tanzania. At Mikumi National Park,
Tanzania, Ramon Rhine and others have been studying yellow baboons since
1974. Yellow baboons have also been studied at Ruaha National Park, Tanzania
and at the Tana River National Primate Reserve, Kenya. There are virtually
no published studies of yellow baboons in Angola, Mozambique, or Malawi,
countries that are plagued by civil war and where it is impossible for scientists
to study baboon behavior.

HABITAT

Yellow baboons inhabit thorn scrub, savanna, open woodland, and gallery
forests
throughout their range (Rowe 1996). At Amboseli National Park, yellow baboons
are found in semi-arid savannas with stands of acacia trees (Acacia xanthophloea and A.
tortilis)
breaking up the open grassland (Altmann & Altmann 1970). Because of the
small amount of rainfall, they require proximity to water sources and are found
in swamps and groundwater forests created from the underground drainage of
Mount Kilimanjaro which rises above the park. Annual rainfall averages 335
mm (1.10 ft) and falls in two distinct periods, from November through December
and March through May. In this marginal environment, the temperature ranges
between 8.89 and 32.2° C (48 and 90° F) (Struhsaker 1967; Bronikowski & Altmann
1996). In the Tana River basin in eastern Kenya where yellow baboons are also
found, mean monthly rainfall is much higher than at Amboseli, around 400 mm
(1.31 ft) and the climate is slightly more temperate with average temperatures
ranging between 22 and 34° C (71.6 and 93.2° F) (Wahungu 1998). The
rainy seasons around the Tana River last from April to May and November to
December, similar to the seasonal pattern at Amboseli (Wahungu 1998). Yellow
baboons that are found in central Tanzania at Mikumi National Park live in
the floodplain of the Mkata River (Norton et al. 1987). A mosaic of riverine
forests and open grassland, which is seasonally flooded, are found in Mikumi
and baboons do not range into the open grassland farther than 2 km (1.24 mi)
from stands of trees. The warm, wet season lasts from November through May
and the cold, dry season begins in June and continues through October. The
average annual rainfall is 842 mm (2.76 ft) and temperatures range from 15
to 35° C (59 to 95° F) (Norton et al. 1987). Water is a limiting
factor for baboon groups. The amount of rain determines the amount of standing
water and therefore dictates the ranging patterns of baboon groups living in
the park (Norton et al. 1987). In addition to being found in undeveloped savannas,
yellow baboons are highly adaptable and can take to living alongside humans
in rural areas developed for agriculture (Maples et al. 1976; Muoria et al.
2003).

ECOLOGY

Baboons have a diverse diet and are able to exploit a wide variety of foods,
a necessity in an environment that is highly seasonal and in which the availability
of food varies in abundance throughout the year. Yellow baboons have been
called "eclectic omnivores,"
because they are extremely selective in their
foraging but
they have a highly diverse diet (Altmann 1998). For example, in a study done
at Mikumi National Park, Tanzania, yellow baboons were recorded eating plant
parts from more than 180 species, but of those, only seven species were eaten
throughout the year (Norton et al. 1987). Yellow baboons are highly dependent
on reliable food sources including two species of acacia -- the fever
tree (Acacia xanthophloea) and the umbrella tree (A.
tortilis) -- grasses,
and tubers (Altmann & Altmann 1970; Post 1982; Norton et al. 1987). In
gallery forests and around permanent water holes, they consume all edible parts
of the fever tree including leaves, gum, inner pith, blossoms, seeds, seed
pods, and rotten wood. The umbrella tree, which grows in drier parts of their
habitat, is utilized in a similar manner (Altmann & Altmann 1970). They
also feed on grasses, stripping the seed heads from the blades and consuming
the most nutritious part of the grass. During the dry season, they dig around
the base of grass blades and consume the corms, which are fleshier and have
more water content than the tips of the blades (Altmann & Altmann 1970).
Immediately following the rainy season, when grass begins to sprout and is
plentiful, they consume the entire blade (Wahungu 1998). Baboons are excellent
diggers and utilize tubers, corms, and underground bulbs of plants throughout
the year as well (Post 1982; Norton et al. 1987). In addition to grass, tubers,
and acacia tree products, yellow baboons also feed on fruits, flowers,
orthopterans,
termites, beetles, ants, reptiles, birds, bird eggs, small vertebrate prey,
and other primates including vervet monkeys (Chlorocebus aethiops)
and lesser bush babies (Galago senegalensis). At the Tana River site where baboons are studied, fruit availability
peaks after the rainy season and is at its lowest toward the end of the dry
season. To cope with these seasonal changes in fruit availability, yellow baboons increase the frequency of consumption of invertebrates as well as eating more roots and tubers (Wahungu 1998).

Yellow baboons are reliant on essential localized resources such as water, food,
and sleeping sites to determine their ranging patterns, therefore seasonal differences
in daily range length and home range size are seen (Altmann 1974). At the Tana River study site, during the
months following the end of the rainy season, baboons spend more time foraging
and moving in gallery forests areas compared to the dry season, when they move
into the open woodland and savanna (Wahungu 1998). The prevalence of fruit in
the forest after the rainy season means they do not have to travel as far to
obtain nutrient-rich foods and their daily path length is only about 3.4 km
(2.11 mi) (Wahungu 2001). In the dry season, when fruits are scarce and foods
in the forest are fewer compared to the savanna, yellow baboons expand their
daily path movements to exploit as many food resources as are available, moving about
7.2 km (4.47 mi) each day (Wahungu 1998; 2001).

While most of the day is spent on the ground, baboons retreat to trees in nearby
riverine or gallery forests overnight. Because of its size, the group is spread
out over several trees, utilizing a sleeping grove rather than just a single
tree (Wahungu 2001). Baboons center their home ranges around the main forested
area where sleeping trees are located and return to the grove in the evenings
(Wahungu 2001). The group leaves the sleeping grove between 7:00 and 10:00 a.m.
each morning. After descending from the trees, the group either remains in the
vicinity of the sleeping grove, socializing and grooming or moves into open
grassland to forage (Altmann & Altmann 1970). Yellow baboons forage throughout
the day, but there are peaks in social activity in the mid-morning, early to
mid-afternoon and in the evening after entering the sleeping grove. As they
forage, the group moves progressively further from the sleeping grove, but
around mid-day, the group turns and begins to forage in the direction of the
sleeping grove, working their way back to the forest and entering the sleeping
grove between 5:30 and 6:45 p.m. (Altmann & Altmann 1970; Wahungu 2001).

SPECIAL NOTES

Baboons appear to be more closely related to humans and are therefore good
candidates for animal models in biomedical research (Fridman & Popova 1988a).
Yellow baboons, in particular, have been used in research on physiology, blood,
the cardiovascular system, neurology, and endocrinology. They have also been
used as an animal model to study organ transplantation, alcoholism, epilepsy,
and high blood pressure (Fridman & Popova 1988b). About 6% of the biomedical
studies involving nonhuman primates include baboon species (Carlsson et al.
2004). Changes in taxonomy and difficulty identifying species have made it
impossible to evaluate which baboon species are used most frequently in research
(Fridman & Popova 1988a).

Disclaimer: The Wisconsin Primate Research Center provides Primate
Info Net as an informational service.We are not responsible for the content of
linked sites, nor does inclusion of a link imply endorsement of the
views expressed in that content.